The Bill of Rights guarantees your right to religious freedom, but I do not see an implied right to be atheist within that Right, nor do I believe it was so intended by the framers of the Constitution.

As a non-American, I look in strange wonder at the way some Americans seem to live the Constitution as much as they do the Bible. Why should the opinions of a bunch of guys hundreds of years ago matter SO MUCH in the 21st century anyway? Surely the fact that there have been 23(iirc) constitutional amendments since then indicates to me that they didn't get it right and that things change... Sheesh.

The Bible's cadre can't admit when they're wrong. The existence of 23 amendments proves that while the Constitution may not have gotten everything right in one go, it actually adapts when it is wrong. The same cannot be said for the Bible. Well, save for King James insisting on drafting the King James translation, poorly, with admonishments about homosexuality somewhat reinforced (Despite having been a confirmed bisexual). Yeah...

And further? There isn't a nation on Earth that doesn't have a founding charter in some form or another, be it a Constitution, a charter, or otherwise. It's a statement of culture, of higher aims, cementing the founding history of the nation. They exist for a bloody good reason.